Fungal Reproduction: Asexual and Sexual Spores

1. MYCOLOGY (MIC 206) CHAPTER 2: REPRODUCTION MDM ASLIZAH MOHD ARIS

2. Reproduction • Filamentous fungi • Asexually by fragmentation of hyphae • Asexual and sexual reproduction by spores • Yeasts • Asexually by budding or fission: • Fission: e.g. Schizosacchromyces pombe. • Budding e.g. Saccharomyces cerevisiae. • Sexual reproduction by spores (in high stress condition)

3. Kingdom Fungi – 4 Major Phyla • Phylum Zygomycota = the Bread Molds • Rhizopus – black bread mold • Phylum Ascomycota = the Sac Fungi • Yeast, morels, truffles • Phylum Basidiomycota = the Club Fungi • Mushrooms, puffballs, bracket fungi, rusts, smuts, toadstools • Phylum Deuteromycota = the Fungi Imperfecti

4. Terms • Fragmentation can occur whereby mycelium are torn apart by external forces and these bits can start new individuals if conditions are favourable. • Fission is a simple splitting of a cell into two new daughter cells by constriction and the formation of a cell wall e.g. yeast. • Budding is the production of small outgrowths (bud) from a parent cell and as the bus is formed, the nucleus of the parent cell divides and one daughter nucleus migrates into the bud. The bud increase in size while still attached to the parent cell and eventually breaks off and forms a new individual. Yeast reproduce via budding but do some other fungi in different conditions.

5. Reproduction • Teleomorphs-produce both sexual and asexual spores • Anamorphs- lost ability to reproduce sexually-Penicillium • belonged to Deuteromycota • now classified as anamorphs of other phyla: rRNA & Woese • most are Ascomycetes

6. ASEXUAL REPRODUCTION

7. Asexual Spores • More important type of reproduction as it occurs several times throughout the season. • Produced by fragmentation of aerial hyphae • Progeny genetically identical to parent

8. Production of spores is most common type of reproduction. • Production of spores where each spore germinate to form a germ tube that grows into the mycelium. • Spores can be of various colours, depending on: • the colour of hyaline (green, yellow, orange, red, brown, black); • shape (oval, oblong, needle-shaped, helical); • number of cells (one to many); • arrangement of cells and where they are situated.

9. Several types of spores: • Conidiospores • Blastospores • Chlamydospores • Sporangiospores • Arthrospores

10. Arthrospores 1A 2 Chlamydospores 1 Conidiospores 3 1B Blastospores Sporangiospores

11. ASEXUAL SPORES Conidiospore • Multiple (chains) or single spores formed at the end of an aerial hypha • Not enclosed within a sac • Eg: Aspergillus spp. and Penicillium spp.

12. Conidial fungus • reproduces by means of asexual spores called conidia • Conidia vary greatly in shape, size and color • Most of the common household molds & mildews are conidial fungi

13. ASEXUAL SPORES (cont.) • Blastospores • A bud coming off the parent cell • Candida albicans Blastospore

15. ASEXUAL SPORES (cont.) • Chlamydospore • Formed within hypha • Thick-walled spore • Candida albicans

16. Chlamydospores • The chlamydospore is a method of producing a substantial resting spore very quickly • Nutrient is shunted from adjacent cells into a preferred cell and it swells up, converts nutrient materials to oil droplets for efficient storage, then rounds off with a thick, often roughened outer wall for protection

17. ASEXUAL SPORES (cont.) • Sporangiospores • Hundreds formed within a sac (sporangium) at the end of an aerial hypha • Rhizopus spp.

19. SEXUAL REPRODUCTION

20. Sexual Reproduction • Union of two nuclei. • The entire thallus can be converted into one or more reproductive structures. • Somatic and reproductive phases do not occur together in the same individual and this is called holocarpic. • In majority of fungi, only a portion of the thallus give rise to reproductive organs and they are called eucarpic.

21. Sexual Reproduction (con’t) Some fungal species produce distinguishable male and female sex organs on each thallus – hermaphroditic or monoecius. These species can reproduce sexually by itself. Other species consist of male or female thalli – dioecious and therefore cannot reproduce itself.

22. The sex organs are called gametangia / gametangium which may differentiate into gametes. • The male gametangium are called antheridia / antheridium and the female are called oogonia / oogonium. • Heterokaryosis – the existence of different kinds of nuclei in the same individual.

23. Sexual Spores • Three phases of development • Plasmogamy: a union of two protoplasts bringing about the nuclei close together and within same cell. - haploid nucleus of a donor cell (+) penetrates the cytoplasm of a recipient cell (-) • Karyogamy:Fusion of the two nuclei. Formation of a dikaryon – a binucleate cell containing two nuclei from each parent - the 2 nuclei fuse to form a diploid nucleus • Meiosis: diploid nucleus gives rise to haploid nuclei - Sexual spores, some + , some -,some recombinants - Sexual spores used to classify fungi into divisions

24. Classification of these groups • First three groups is based on their method of sexual reproduction • 4th group, the Deuteromycetes, have NO sexual reproduction

25. ZYGOMYCOTA

26. Zygomycota (Conjugation Fungi) • Also known as bread molds. • Saprophytic molds with coenocytic hyphae (lack septa). • Asexual Reproduction: Used most of the time. Sporangiospore: Asexual spore enclosed within a sporangium or sac at the end on an aerial hypha. • Sexual Reproduction: Occurs through conjugation, the joining of hypha of two different strains (plus and minus). Zygospores: Sexual spores which are enclosed in a thick, resistant wall. • Generally not pathogens. Rhizopus stolonifer: Common black bread mold. May cause opportunistic infections in diabetes patients

27. Zygomycota – common molds The fungal mass of hyphae, known as the MYCELIUM penetrates the bread and produces the fruiting bodies on top of the stalks. Mycelia = a mass of hyphae or filaments

28. Rhizoids = root-like hyphae The zhizoids meet underground and mating occurs between hyphae of different molds (SEXUAL REPRODUCTION)

29. Zygomycota (Rhizopus)

31. Lifecycle of a Zygomycete Fungi – Asexual then Sexual

32. Reproductive Structures of Zygomycete (Rhizopus)Sporangia (asexual) and Zygospore (sexual)

33. ASCOMYCOTA

34. Ascomycota (Sac Fungi) • Molds with septate hyphae and some yeasts. • Asexual Reproduction: Conidiospores not enclosed in a sac. Become airborne easily. Form chains (broom-like structures). • Sexual Reproduction: Ascospores enclosed in a sac-like structure (ascus). • Include common antibiotic producing fungi and yeasts, and several human pathogens. • Penicillium notatum (Produces penicillin) • Saccharomyces (Brewer’s yeast) • Trychophyton (Athlete’s foot) • Aspergillus (Carcinogenic aflatoxin in peanuts),

35. Ascomycota – Cup Fungi Life Cycle

36. BASIDIOMYCOTA

37. Basidiomycota (Club Fungi) • Have septate hyphae. • Include mushrooms, toadstools, rusts, and smuts. • Sexual Reproduction: Produce basidiospores: Spores formed externally on a club shaped sexual structure or base called basidium. • Asexual Reproduction: Through hyphae. • Examples: • Amanita: Mushroom produces lethal toxins to humans. • Claviceps purpurea: Produces ergot toxin in wheat and rye.

38. Bracket Fungi Puff Balls Basidiomycete Fungi that all produce Basidiospores Jelly Fungi Mushrooms

39. Other Basidiomycetes Rusts and Smuts Rust infecting wheat leaves Whitrot Smut digesting old wood Rust infecting a Leaf

40. Life Cycle of Basidiomycete Fungi

41. DEUTEROMYCOTA

42. Deuteromycota (Imperfect Fungi) Regarded as imperfect because they exhibit no sexual stage has been observed in their life cycle

43. Deuteromycota – the Fungi Imperfecti • Resemble Ascomycetes, but their reproductive cycle has never been observed • Different from Ascomycetes because there is a definite lack of sexual reproduction, which is why they are called Imperfect Fungi Penicillium fungi Up Close

44. PARASEXUAL REPRODUCTION

45. Parasexual Reproduction This phenomenon occurs whereby the three steps in sexual reproduction take place not at specific points in the life cycle. Several Ascomycota species are not known to have a sexual cycle. Such asexual species may be able to undergo genetic recombination between individuals by processes involving heterokaryosis and parasexual events. Parasexuality refers to the process of heterokaryosis, caused by merging of two hyphae belonging to different individuals, by a process called anastomosis, followed by a series of events resulting in genetically different cell nuclei in the mycelium.

46. QUESTIONS Differentiate between the types of spores. Differentiate between the different types of asexual reproduction. Name one (1) fungus that has a parasexual type of reproduction.